Donald Tusk is the victor on the Vistula, Poland's pre-eminent politician, untroubled by opposition or dissent on the domestic stage. Re-elected late last year with an enhanced majority, Tusk does not even have to worry about the voters.

The prime minister is clearly aware of his impregnable position. So sure of himself in fact that he openly humiliates party rivals whom once he might have tolerated. He has also given up his former reticence over attacking the opposition, and now goes at them in a manner that has been described as below the belt.

As communism fell apart at the end of the 1980s, Tusk belonged to a group of young intellectuals around the Solidarity union who saw Poland's place in the European union. After 1989, he became one of the leading lights of the liberal movement, which espoused the market economy and declared war on the state bureaucracy. He agitated for an end to prejudice and wrote a book about the good interactions between Germans and Poles in the city of Gdansk, before it became a 20th-century bone of contention.

But Tusk was to discover that his vision of modernisation was a bit too radical for the majority. The liberals were politically marginalised and it took him years to find his way back into the political big time. He transformed himself into a conservative and made his peace with the Catholic church, finally having his civil partnership blessed in church. These days, he demands a strong state; his old mantra about slimming it down has long since been forgotten. He also does not let himself get deflected by issues such as the church's place in society or the ban on abortion, because he doesn't want to get bogged down in battles he knows he can't win.

Instead, his absolute priority is Poland's deeper integration into Europe. If there is such a thing in Poland as a pro-European, Tusk is it. He stresses at every opportunity that a well-functioning EU lies in Poland's interests. The overwhelming majority of his compatriots see things the same way. They understand that Poland is a big beneficiary of the EU's internal largesse – Poland is by some distance the biggest net receiver of EU funding. Even provincial folk who once were nervous of the EU have come round. Farmers benefit from strong demand for foodstuffs from other EU countries.

But this concept brings its own difficulties. Tusk, who speaks good German, has taken up close collaboration with the Germans, something a large proportion of his countrymen view with some scepticism.

He has long been on familiar terms with Angela Merkel. While the first-ever Polish president of the EU in the second half of last year, he supported the position of the German chancellor, who demanded austerity measures from the crisis-hit EU countries. But at the same time, his government tried to build an alliance of EU nations who are net recipients from the EU budget, against net contributor nations.

Berlin and Paris were not pleased. Tusk cannot afford a diminution of EU funds for Poland. In his first term in office, Poland's budget deficit more than doubled. He is therefore two things: a European from inner conviction, and out of need.

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